1. Field of the Invention
The present invention relates to a folder gluer, and more particularly to a folder gluer for folding and joining a cardboard sheet having four panels and a glue tab.
2. Description of the Related Art
In general, cardboard sheet box-forming machines perform slotting and creasing; slots and creases are formed on cardboard sheets extending in the feed direction. Cardboard sheets for forming a box have four panels and a glue tab. A folder gluer is one processing device within a cardboard box making machine, by which two panels in a cardboard sheet are folded 180° and that folded single panel is glued to a glue tab. Two panels are folded by being brought into contact with a folding bar or a folding belt as a cardboard sheet is fed at high speed. During this folding, the two panels spread apart on the upstream side in the feed direction due to contact friction resistance with the folding belt or the like, splaying in fishtail form so that their folding direction skews away from the creases formed on the cardboard sheet.
In order to correct for the above fishtail-splaying folded portion after the fact, the conventional folder gluer disclosed in JP-2007-185799A is furnished with a pair of pressing plates movable in the width direction of the sheet, perpendicular to the feed direction. The pair of pressing plates press the splayed folded portions in the sheet width direction. A sensor is placed upstream of the pair of pressing plates in the feed direction, and detects the passing of the front edge of the cardboard sheet. After the elapse of a predetermined time following detection of passage of the front edge of the cardboard sheet by the sensor, the pair of pressing plates move in the sheet width direction and apply an instantaneous strong pressure to the outside edge of the folded portions. In the folder gluer of JP-2007-185799A described above, the instantaneous pressing operation by the pair of pressing plates is carried out after the two panels on each side of the cardboard sheet are folded to 180° and before the two panels are glued on the glue tab.